A vacuum system for amateur home winemaking
David W. Vehar
There are a number of pre-built vacuum systems available for the home winemaker, and there is no reason to disparage any of these. However, during my 40-year career as an engineer making equipment work in a laboratory, I have found it considerably more satisfying to design and build something myself than to purchase it. Besides, after said 40-year career, I prefer to avoid heavy lifting. So, a few years ago when my wife presented me with a home winemaking kit, I immediately started to think of ways to make the material handling easier.
The first of these innovations was a hydraulic lift to hold my carboys, which allowed me to raise or lower them as needed. This actually worked pretty well, but still involved working at inconvenient heights. My next idea was to use a vacuum to pump the wine, allowing me to work at a convenient bench top height without having to lift carboys from floor level. I also thought that with fewer components actually touching the wine, sanitizing and cleanup would be easier. I immediately discovered a number of systems described for just that purpose. This was obviously not a novel idea, but I persisted.
So, nearly five years and 30 kits later, virtually every stage of my wine handling is now done with vacuum. The following is a description of the various components that go into my system. There is little unique about this setup. This is what I have found works for me, and it continues to evolve with experience and the suggestions of others.
A generalized view of the vacuum system is shown in the accompanying diagram. A pump creates a vacuum that draws wine from a fermenter or supply carboy into a sealed receiving vessel (carboy or wine bottle) by means of a racking cane and 3/8” ID Tygon® tubing. All other tubing is 1/2″ OD x 3/8” ID, either Tygon® or HDPE (high density polyethylene) tubing. These will not collapse under vacuum. A trap placed between the receiving carboy and the pump prevents liquids from entering the pump. Details of the individual components and how they are used are provided below.
For reference, atmospheric pressure (1 atmosphere) = 14.7 psi = 29.9 inHg at sea level (24 inHg at 6000 ft where I live). Attainable vacuum depends on the type of pump, but this is the maximum that any pump can produce.
My pump is a GAST® LOA-P175 oil-less rocking piston pump capable of maximum vacuum of 26 inHg, or about 20 inHg at 6000 ft. I found it new on eBay for about $120, salvaged from a beverage handling system. This is adequate for vacuum degassing, and is more than adequate for transferring liquids (racking). I equipped the pump with a vacuum valve and vacuum gauge purchased from my local Granger store.
There are a number of inexpensive utility pumps available for applications such as servicing air conditioning systems. Most of these are oil-lubricated. I chose an oil-less pump because I have never found an oil-lubricated pump that didn’t exhaust some oil into the air. I don’t want to breath it, and I certainly don’t want it to find its way into my wine. [Ed note – Medical vacuum pumps like those manufactured by Schuco and others are also a popular choice. ]
The purpose of a vacuum trap is to prevent liquids from entering the pump, potentially damaging it. This consists of a container to trap any liquids that might be pulled in by the vacuum, before they can enter the pump.
HDPE vacuum bottles are readily available from suppliers such as US Plastics, but I assembled mine from 4” PVC pipe fittings from a local hardware store. A 4” schedule 40 PVC-DWV female NPT to SPG adapter is fitted to a PVC-DWV hub cap, and solvent welded to form a vacuum-tight cylinder. Threads are coated with vacuum grease to ensure a good seal, and to make opening and closing the container easier. For easy disconnect and to facilitate cleaning, I drilled and tapped holes for bayonet vacuum fittings. Hose barbs would be equally functional. For the vacuum fittings, see http://www.usplastic.com/catalog/item.aspx?itemid=83680&catid=926
Vacuum racking requires sealing a receiving carboy so that it can maintain a vacuum, and drawing the liquid from the supply carboy or fermenter through tubing and a racking cane. The supply carboy must not be sealed. Depending on where my wine is in its process, I rack into either a standard glass carboy or a glass Big Mouth Bubbler® carboy. The carboy closures are different, but the process is the same.
Because they are easier to clean, I normally use the Big Mouth Bubbler for secondary fermentation and clearing/stabilization, where a significant amount of sediment is expected. The manufacturer has recently introduced its “Universal Single Port” and “Universal Dual Port” lids. The ports are sized to accommodate a standard tapered carboy stopper. The dual port version allows for a vacuum to be drawn from one port while wine enters the carboy through the other port. As the supply carboy or fermenter nears empty, the vacuum can pull air through the racking cane and into the wine in the receiving carboy. A shutoff valve located just before the wine enters the receiving carboy is used to prevent this.
I use a standard narrow neck carboy for subsequent racking and for long-term storage, where exposure to air can be a significant issue. Racking into a standard carboy is done with an “Orange Universal Carboy Cap”. Vacuum is applied through the side tube, while the wine is drawn into the carboy via a racking tube through the center of the cap.
Safety note: Under normal circumstances, the vacuum in the receiving carboy will be between 5 and 10 inHg because the supply carboy is open to atmosphere. If the racking cane becomes plugged, however, the receiving carboy can reach the full vacuum produced by the pump. While I have not heard of carboys imploding, carboys are not vacuum rated and no data exists regarding safe levels. Containment and blanketing of carboys under vacuum is recommended. I use carboy covers from http:/www.carboy.net and a plastic tub for this purpose. Also note that the PET (plastic) carboys commonly available from winemaking suppliers should never be used as receiving carboys because they will collapse under vacuum.
Wine kits are designed to be completed within 4-8 weeks, which does not give wine time to degas and clear on its own. Hence, all wine kits will have instructions for degassing and fining the wine. Because CO2 can prevent the fining agents from binding to particulates in the wine, it is necessary to degas either before or in conjunction with the addition of the fining agents.
Vacuum is applied to a sealed carboy, with frequent agitation to allow dissolved CO2 to come to the surface. I find this to be an inefficient way of degassing, and at least one study has shown aggressive stirring to be more effective. See Pambianchi’s article
However, as discussed in the previous section, degassing occurs naturally during racking. CO2 is released from the wine and drawn off under vacuum as the wine flows into the receiving carboy. Once the racking is complete, very little additional CO2 is released. Some wine kits have you stir the sediment back into the wine before racking, adding the fining agents and degassing at the same time. I accomplish this by first stirring the sediment back into the wine, and then racking/degassing into a clean carboy and adding the fining agents.
This is probably the trickiest part of a vacuum-does-all system because the vacuum needs to be applied bottle-by-bottle, at the same time controlling the fill level. Using a container with a sufficient number of cleaned and sanitized bottles to complete a batch, all of the bottles are filled before corking is done. A fill tool is inserted into a bottle and pressed against the bottle rim to form a seal. Using a thumb or finger, the vacuum vent hole is covered, allowing a vacuum to form and wine to flow into the bottle. When the wine level reaches the level of the hole in the fill tube, the vacuum vent hole is released and excess wine siphons back into the supply tubing. The level of the wine adjusts automatically when the fill tool is removed. For this to work properly, the fill tool must be slightly higher than the level of the wine in the carboy. The fill tool is then moved to the next bottle, and filling continues until the carboy is empty.
I assembled my bottle filling tool largely from PVC parts available at a local hardware store. The components, necessary modifications, and final assembly are described below. All parts are plastic or stainless steel, able to withstand the harsh chemicals (PBW® and Starsan®) used for cleaning and sanitizing.
- The body of the fill tool is a 1” schedule 40 PVC tee with a 1/2” NPT threaded side port to accommodate a barbed fitting for vacuum. A 5/16” hole is drilled through the side port (and the barbed fitting), creating a vacuum vent.
- The top cap is a 1” PVC plug, drilled and tapped with 1/4” NPT threads to accommodate a barbed fitting for the wine stream.
- A stainless steel 3/8” tube OD x 1/4″ female NPT adapter, Swagelok® part number SS-600-7-4, allows a 2” long 3/8” OD stainless steel tube to be threaded onto to the portion of the barb that extends through the top cap. This assembly is inserted (dry fit) into the top of the fill tube body. If these stainless steel parts are not available, other plastic fittings are available that will accomplish the same function. For example, a 3/8” PF x 1/4″ FIP push-connect fitting, Proline 640-302BG, will also work, with 3/8” OD HDPE (polyethylene) tubing instead of stainless steel. Do not use brass.
- A 1/4” ring cut from 1” schedule 40 PVC pipe is inserted (dry fit) into the bottom of the fill tool body, followed by a 1” O-ring or gasket. This forms a seat for the rim of the bottle during filling.
- An HDPE extension tube, 3/8” ID, approximately 8” long, is slipped onto the stainless tube. This tube has a 1/4” hole drilled into the side approximately 2” from the top. In conjunction with the displacement of wine by the tube itself, this hole will define the fill level in the bottle and is adjusted by slipping the HDPE extension tube up or down on the stainless tube.
It is suggested that a trial using water be done prior to bottling to establish the desired fill level. Also, if the flow rate into the bottles is too high for easy control, flow can be restricted to a convenient level with a tubing flow control clamp.
Shortcomings of an all-vacuum system
Although the use of vacuum can make many parts of the winemaking process easier, it cannot be used for everything. Unfortunately, the vacuum system will not yet clean my carboys for me.